AOP 实战四件套：日志、权限、限流与缓存切面

package com.example.anno;import java.lang.annotation.*;@Target(ElementType.METHOD)          // 贴在方法上@Retention(RetentionPolicy.RUNTIME)  // 运行期可读，切面才拿得到@Documentedpublic @interface OpLog {    String value() default "";       // 操作描述，如「删除用户」    boolean recordArgs() default true;   // 是否记录入参}

package com.example.aspect;import com.example.anno.OpLog;import org.aspectj.lang.ProceedingJoinPoint;import org.aspectj.lang.annotation.*;import org.aspectj.lang.reflect.MethodSignature;import org.slf4j.*;import org.springframework.stereotype.Component;import org.springframework.web.context.request.*;import jakarta.servlet.http.HttpServletRequest;import java.util.Arrays;import java.util.UUID;@Aspect@Componentpublic class OpLogAspect {    private static final Logger log = LoggerFactory.getLogger(OpLogAspect.class);    @Around("@annotation(opLog)")    public Object around(ProceedingJoinPoint pjp, OpLog opLog) throws Throwable {        // 生成 traceId，串联这一次请求的所有日志        String traceId = UUID.randomUUID().toString().substring(0, 8);        MDC.put("traceId", traceId);        long start = System.nanoTime();        String op = opLog.value().isEmpty()                ? ((MethodSignature) pjp.getSignature()).getMethod().getName()                : opLog.value();        try {            Object result = pjp.proceed();            if (opLog.recordArgs()) {                log.info("[{}] 操作={} 参数={} 返回={} 耗时={}ms 操作人={}",                        traceId, op, Arrays.toString(pjp.getArgs()), result,                        (System.nanoTime() - start) / 1_000_000, currentUser());            }            return result;        } finally {            MDC.clear();   // 线程复用场景下必须清理，否则 traceId 串味        }    }    private String currentUser() {        ServletRequestAttributes attrs =                (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();        if (attrs == null) {            return "system";   // 异步 / 定时任务里没有请求上下文        }        HttpServletRequest req = attrs.getRequest();        Object user = req.getSession().getAttribute("LOGIN_USER");        return user == null ? "anonymous" : user.toString();    }}

package com.example.exception;public class ForbiddenException extends RuntimeException {    public ForbiddenException(String message) {        super(message);    }}

package com.example.aspect;import com.example.anno.RateLimit;import com.example.exception.TooManyRequestsException;import org.aspectj.lang.annotation.*;import org.springframework.stereotype.Component;import java.util.Map;import java.util.concurrent.ConcurrentHashMap;@Aspect@Componentpublic class RateLimitAspect {    // key = 方法标识 + 调用方，value = 当前窗口的计数与起点    private final Map<String, Window> windows = new ConcurrentHashMap<>();    @Around("@annotation(rateLimit)")    public Object limit(ProceedingJoinPoint pjp, RateLimit rateLimit) throws Throwable {        String key = pjp.getSignature().toShortString() + "|" + CurrentUser.id();        long now = System.currentTimeMillis();        long span = rateLimit.seconds() * 1000L;        Window w = windows.compute(key, (k, old) -> {            if (old == null || now - old.start >= span) {                return new Window(now, 1);   // 新窗口，计数从 1 开始            }            old.count++;            return old;        });        if (w.count > rateLimit.limit()) {            throw new TooManyRequestsException("请求过于频繁，请稍后再试");        }        return pjp.proceed();    }    private static final class Window {        final long start;        int count;        Window(long start, int count) {            this.start = start;            this.count = count;        }    }}

package com.example.aspect;import com.example.anno.MyCache;import org.aspectj.lang.ProceedingJoinPoint;import org.aspectj.lang.annotation.*;import org.aspectj.lang.reflect.MethodSignature;import org.springframework.core.DefaultParameterNameDiscoverer;import org.springframework.expression.*;import org.springframework.expression.spel.standard.SpelExpressionParser;import org.springframework.expression.spel.support.StandardEvaluationContext;import org.springframework.stereotype.Component;import java.util.Map;import java.util.concurrent.ConcurrentHashMap;@Aspect@Componentpublic class MyCacheAspect {    private final ExpressionParser parser = new SpelExpressionParser();    private final DefaultParameterNameDiscoverer names = new DefaultParameterNameDiscoverer();    private final Map<String, Entry> store = new ConcurrentHashMap<>();    @Around("@annotation(myCache)")    public Object cache(ProceedingJoinPoint pjp, MyCache myCache) throws Throwable {        MethodSignature sig = (MethodSignature) pjp.getSignature();        String key = sig.toShortString() + "#" + resolveKey(myCache.key(), sig, pjp.getArgs());        Entry hit = store.get(key);        long now = System.currentTimeMillis();        if (hit != null && now - hit.time < myCache.ttl() * 1000L) {            return hit.value;   // 命中：直接返回，目标方法不执行        }        Object value = pjp.proceed();   // 未命中：执行目标方法        store.put(key, new Entry(value, now));        return value;    }    private String resolveKey(String spEL, MethodSignature sig, Object[] args) {        StandardEvaluationContext ctx = new StandardEvaluationContext();        String[] params = names.getParameterNames(sig.getMethod());        for (int i = 0; params != null && i < params.length; i++) {            ctx.setVariable(params[i], args[i]);        }        return String.valueOf(parser.parseExpression(spEL).getValue(ctx));    }    private record Entry(Object value, long time) {}}

@Aspect@Order(1)@Componentpublic class OpLogAspect { /* 最外层：日志 */ }@Aspect@Order(2)@Componentpublic class RateLimitAspect { /* 次外层：限流 */ }@Aspect@Order(3)@Componentpublic class PermAspect { /* 中间层：权限 */ }

// 正确写法：记录后原样抛出，让事务拿到异常才能回滚@Around("@annotation(opLog)")public Object right(ProceedingJoinPoint pjp, OpLog opLog) throws Throwable {    try {        return pjp.proceed();    } catch (Throwable e) {        log.error("方法执行失败", e);        throw e;              // 关键：继续向上抛，事务边界才能感知失败    }}

[COST] 下单 耗时=51ms 阈值(warn=200, error=1000)[COST] 对账 耗时=301ms 阈值(warn=20, error=1000)[COST] 报表 耗时=151ms 阈值(warn=200, error=100)[SUMMARY] 下单=1次/51ms 对账=1次/301ms 报表=1次/151ms